Freeze desiccation of foods is based on the use of a solid desiccant for the adsorption of water vapor which sublimes from the frozen food at a reduced pressure. Desorption isotherms of the food and adsorption isotherms of the desiccant were used for the calculation of the quantities of desiccant necessary to obtain different pre-determined residual moisture contents of the food. An equation and a curve were developed for this purpose. The new method compares favorably with conventional freeze dehydration. It offers the specific advantages of accurate control of the end point residual moisture in the food. For moisture contents above about 5%, the use of silica gel as a desiccant was found to be very suitable. For moisture contents below this limit, substitution of molecular sieves for the silica gel in a two-stage desiccation process was necessary in order to desorb the more firmly bound water.